package com.brsya.base.util;

import java.security.Key;
import java.security.Security;

import javax.crypto.Cipher;

/**
 * Created by Zhuwenbin on 2020/7/3.
 * Email:276776313@qq.com
 * Description:
 */
public class DesUtil {

    private static String strDefaultKey = null;    //默认的密钥，根据情况修改
    private Cipher encryptCipher = null;
    private Cipher decryptCipher = null;

    /**
     * 使用默认密钥进行DES加密
     */
    public static String encrypt(String plainText) {
        try {
            return new DesUtil().encryptDES(plainText);
        } catch (Exception e) {
            return null;
        }
    }


    /**
     * 使用指定密钥进行DES解密
     */
    public static String encrypt(String plainText, String key) {
        try {
            return new DesUtil(key).encryptDES(plainText);
        } catch (Exception e) {
            return null;
        }
    }


    /**
     * 使用默认密钥进行DES解密
     */
    public static String decrypt(String plainText) {
        try {
            return new DesUtil().decryptDES(plainText);
        } catch (Exception e) {
            return null;
        }
    }


    /**
     * 使用指定密钥进行DES解密
     */
    public static String decrypt(String plainText, String key) {
        try {
            return new DesUtil(key).decryptDES(plainText);
        } catch (Exception e) {
            return null;
        }
    }


    /**
     * 默认构造方法，使用默认密钥
     *
     * @throws Exception
     */
    private DesUtil() throws Exception {
        this(strDefaultKey);
    }


    /**
     * 指定密钥构造方法
     *
     * @param strKey 指定的密钥
     * @throws Exception
     */
    private DesUtil(String strKey) {
        if (strDefaultKey == null) {
            strKey = KeyUtil.getKeyString();
            strDefaultKey = strKey;
        }
        try {
            Security.addProvider(new com.sun.crypto.provider.SunJCE());
            Key key = getKey(strKey.getBytes());
            encryptCipher = Cipher.getInstance("DES");
            encryptCipher.init(Cipher.ENCRYPT_MODE, key);
            decryptCipher = Cipher.getInstance("DES");
            decryptCipher.init(Cipher.DECRYPT_MODE, key);
        } catch (Exception e) {
            e.printStackTrace();

        }
    }


    /**
     * 加密字符串
     *
     * @param strIn 需加密的字符串
     * @return 加密后的字符串
     * @throws Exception
     */
    private String encryptDES(String strIn) throws Exception {
        return byteArr2HexStr(encryptDES(strIn.getBytes()));
    }


    /**
     * 加密字节数组
     *
     * @param arrB 需加密的字节数组
     * @return 加密后的字节数组
     * @throws Exception
     */
    private byte[] encryptDES(byte[] arrB) throws Exception {
        return encryptCipher.doFinal(arrB);
    }


    /**
     * 解密字符串
     *
     * @param strIn 需解密的字符串
     * @return 解密后的字符串
     * @throws Exception
     */
    private String decryptDES(String strIn) throws Exception {
        return new String(decryptDES(hexStr2ByteArr(strIn)));
    }


    /**
     * 解密字节数组
     *
     * @param arrB 需解密的字节数组
     * @return 解密后的字节数组
     * @throws Exception
     */
    private byte[] decryptDES(byte[] arrB) throws Exception {
        return decryptCipher.doFinal(arrB);
    }


    /**
     * 从指定字符串生成密钥，密钥所需的字节数组长度为8位
     * 不足8位时后面补0，超出8位只取前8位
     *
     * @param arrBTmp 构成该字符串的字节数组
     * @return 生成的密钥
     * @throws Exception
     */
    private Key getKey(byte[] arrBTmp) throws Exception {
        byte[] arrB = new byte[8];
        for (int i = 0; i < arrBTmp.length && i < arrB.length; i++) {
            arrB[i] = arrBTmp[i];
        }
        Key key = new javax.crypto.spec.SecretKeySpec(arrB, "DES");
        return key;
    }


    /**
     * 将byte数组转换为表示16进制值的字符串，
     * 如：byte[]{8,18}转换为：0813，
     * 和public static byte[] hexStr2ByteArr(String strIn)
     * 互为可逆的转换过程
     *
     * @param arrB 需要转换的byte数组
     * @return 转换后的字符串
     * @throws Exception 本方法不处理任何异常，所有异常全部抛出
     */
    private static String byteArr2HexStr(byte[] arrB) throws Exception {
        int iLen = arrB.length;
        StringBuffer sb = new StringBuffer(iLen * 2);
        for (int i = 0; i < iLen; i++) {
            int intTmp = arrB[i];
            while (intTmp < 0) {
                intTmp = intTmp + 256;
            }
            if (intTmp < 16) {
                sb.append("0");
            }
            sb.append(Integer.toString(intTmp, 16));
        }
        return sb.toString();
    }


    /**
     * 将表示16进制值的字符串转换为byte数组，
     * 和public static String byteArr2HexStr(byte[] arrB)
     * 互为可逆的转换过程
     *
     * @param strIn 需要转换的字符串
     * @return 转换后的byte数组
     * @throws Exception 本方法不处理任何异常，所有异常全部抛出
     */
    private static byte[] hexStr2ByteArr(String strIn) throws Exception {
        byte[] arrB = strIn.getBytes();
        int iLen = arrB.length;
        byte[] arrOut = new byte[iLen / 2];
        for (int i = 0; i < iLen; i = i + 2) {
            String strTmp = new String(arrB, i, 2);
            arrOut[i / 2] = (byte) Integer.parseInt(strTmp, 16);
        }
        return arrOut;
    }


}
